Navien Premium Efficiency (NPE) tankless water heaters are available in four output sizes, with or without built-in recirculation. NPE-A (Advanced) features ComfortFlow recirculation, including a pump and buffer tank, as well as six different pump control options. NPE-S (Standard) tops the Energy Star rating list with up to 0.99EF. All sizes have dual stainless steel heat exchangers and come with a 15-year residential warranty.
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